“On December 28, 1817,” writes Stanley Plumly, “the painter Benjamin Robert Haydon hosts what he refers to in his diaries and ‘Autobiography’ as the ‘immortal dinner.’ The stated reasons for the dinner are, one, that Haydon wants to introduce his young friend John Keats to the great William Wordsworth, and, two, that Haydon wishes to celebrate his progress on his most important and largest historical painting so far, ‘Christ’s Entry into Jerusalem.’ ”

This meeting of the two poets — self-important Wordsworth just past his creative prime, handsome young Keats only starting to write the poems of his too brief maturity — is an iconic moment in the history of English literature. Add the presence of the drunken, whimsical Charles Lamb (who, a few years later, will begin to produce his “Essays of Elia”), a doomed African explorer named Joseph Ritchie, a fatuous government official and the deeply ambitious, self-regarding Haydon himself and you certainly have the makings for, at the very least, a highly memorable evening.

You also have the springboard for this wide-ranging, digressive, lyrical, meditative, repetitive and deeply considered book by poet Stanley Plumly. Do not, in any way, expect “The Immortal Evening” to be a bright, sparkly account of a bright, sparkly dinner party. This is, in fact, an essay on mortality as much as immortality.